This invention relates to a method for controlling the electronic distribution of braking force for a vehicle.
Traditionally, a method for controlling the electronic braking force distribution initiates control only when the rear wheel speed is slower relative to the front wheel speed. However, under this method, when a quick, hard brake pedal action is applied, an initial control point may be delayed, which can cause larger slip in the rear wheels and could prevent accurate electronic braking force distribution control.
An object of this invention is to provide an appropriate initiation of electronic braking force distribution control.
This invention is a method for controlling an electronic braking force distribution in a hydraulic device for a vehicle braking system, which comprises a hydraulic unit comprising a main hydraulic circuit which connects a master cylinder and a wheel cylinder via an inlet valve and an auxiliary hydraulic circuit which connects the wheel cylinder and an auxiliary reservoir via an outlet valve and an electronic control device which controls the hydraulic unit, the method comprising the steps of: determining a degree of pressure applied on the brake pedal, determining estimated vehicle deceleration or vehicle wheel deceleration, controlling the inlet valve and the outlet valve for the rear wheels of the vehicle when the estimated vehicle deceleration or the vehicle wheel deceleration becomes larger than a threshold deceleration value upon pressing the brake pedal, for the purpose of conducting the electronic braking force distribution control, and changing the threshold deceleration value by the degree of the pressure applied on the brake pedal.
This invention further is a method for controlling the electronic braking force distribution as above, wherein the braking force distribution control is initiated when the estimated vehicle deceleration or the vehicle wheel deceleration becomes larger than the threshold deceleration value and the rear wheels slip ratio relative to the estimated vehicle speed becomes larger than a predetermined slip value.
This invention still further is a method for controlling the electronic baking force distribution as above, wherein in the case that, upon pressurizing the brake pedal, the variations in the estimated vehicle deceleration or the vehicle wheel deceleration become larger than a predetermined deceleration value and continue to be larger than a predetermined deceleration value for a predetermined time, the threshold deceleration value for the estimated vehicle deceleration or the vehicle wheel deceleration is set to be smaller than when the variations in the estimated vehicle deceleration or the vehicle wheel deceleration become smaller than that predetermined deceleration value or do not continue to be larger than that predetermined deceleration value for that predetermined time.
This invention yet further is a method for controlling the electronic braking force distribution as above, wherein the case that, upon pressing the brake pedal, the variations of estimated vehicle deceleration or the vehicle wheel deceleration become larger than the predetermined deceleration value or do not continue to be larger than the predetermined deceleration value for the predetermined time, the electronic braking force distribution control is initiated when the estimated vehicle deceleration or the vehicle wheel deceleration becomes larger than the predetermined deceleration value and the rear wheel slip relative to front wheel is larger than the predetermined slip value.
This invention yet further is a method for controlling the electronic braking force distribution as above, wherein the case that, upon pressurizing the brake pedal, the variations of the estimated vehicle deceleration or the vehicle wheel deceleration are larger than the predetermined deceleration value and continue to be larger than the predetermined deceleration value for the predetermined time, the predetermined value of rear wheel slip ratio is set smaller than the rear wheel slip ratio relative to the front wheels when the variations are smaller than the predetermined deceleration value or do not continue to be larger than the predetermined deceleration value for the predetermined time.